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Title: Incremental pluton growth : building of large magma chambers
Author: Schöpa, Anne K.
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2013
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Numerical models of conductive heat flow have been used to explore the connection between incremental pluton growth and large magma chambers. The simulations include repeated sill injections of melt into the crust using variable repose times in between these injections. Adopting this novel approach of a changing magma flux during the emplacement time of a pluton, different intrusion scenarios are tested to constrain the conditions for melt accumulation in the crust during progressive pluton growth. Results reveal that only a rapid increase in magma flux above a background value representative for plutons can lead to the formation of magma reservoirs. Field observations, image analysis (lA) with the intercept method and an anisotropy of magnetic susceptibility (AMS) study are conducted in the silicic Lago della Vacca Complex (LVC) in the Adamello Batholith, northern Italy, to gain insight into magmatic and magnetic fabrics. Combining this data enabled a detailed emplacement scenario for the LVC to be developed. Furthermore, a comparison between the results of lA and AMS shows that these methods are consistent, thus emphasising the applicability of lA and AMS in silicic rocks to reconstruct intrusion emplacement. This is the first comprehensive comparison between AMS and mineral fabrics, obtained by field measurements, lA and computer-assisted X-ray micro-tomography (X-ray /LCT) of which we are aware. The X-ray /LCT images provide the base to acquire the shape-preferred orientation (Spa) of magnetites and mafic silicates, and the spatial distribution of magnetites in a sample. Results show that the AMS signal is consistent with the spa of magnetite grains and clusters but differs from the distribution of the magnetites, suggesting that the AMS is controlled by magnetite grain shape. Moreover, the AMS agrees with the field measurements, lA and the spa of the mafic silicates underlining that lA and AMS can be applied to characterise fabrics in ferromagnetic granitoids. III
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available